Conventionally, to provide a beauty effect such as moisturizing of the skin or to cool or reduce inflammation of an affected area, a sheet-like external preparation that is to be attached to the skin in use has been used.
As such an external preparation, particularly in the field of cosmetics, sheet packs in which nonwoven fabric or the like is impregnated with an aqueous solution of an active ingredient are generally used, but this type of preparation has problems in the retention of water containing an active ingredient and sense of use.
In recent years, the following two types have therefore attracted attention as a more effective sheet-like external preparation.
The first type is an external preparation in which an active ingredient is retained in a gel sheet using a polysaccharide such as agar, carrageenan, locust bean gum, and mannan.
As a sheet-like external preparation of this type, for example, Patent Literature 1 (Japanese Unexamined Patent Application Publication No. H08-290051) discloses a hydrogel base obtainable by blending glucomannan and locust bean gum or carrageenan. The hydrogel base is very unlikely to lose shape and stable in a weakly acidic region including the human skin.
In addition, Patent Literature 2 (Japanese Unexamined Patent Application Publication No. 2002-87993) discloses an external gel composition containing carrageenan and/or mannan, and a polysaccharide thickener (for example, gellan gum, agar, and agarose) that can alone form a gel with a melting point of 80° C. or higher. The external gel composition has an excellent sense of use and appearance and high storage stability.
Moreover, Patent Literature 3 (Japanese Unexamined Patent Application Publication No. 2009-67765) discloses that a water-soluble gel for mask having a total blending amount of carrageenan and locust bean gum of 2.0% by weight or less is excellent in form retention and flexibility and is easily attached by adhering to provide adhesion.
Also, the second type is an external preparation having a dry film-like sheet containing a water-soluble substance such as a cellulose derivative, starch, and sugar as an active ingredient. For this type of external preparation, after the sheet is attached to the skin, water is added to dissolve the film and thereby an active ingredient is supplied to the skin.
The above gel sheet has such advantages that the gel is retained in a sheet-like form and thus stable and easy to handle, and the gel sheet tightly adheres to the skin due to retention of water in the gel. On the other hand, the high form retention of the gel sheet has made it difficult to dissolve the active ingredient in the gel into the skin as intended.
In addition, in the case of a dry film-like sheet, when the film is dissolved, all the active ingredients in the film can be supplied to the skin. However, the adhesion of the film to the skin is poor, and the film is dissolved easily when water is supplied. This type of film has had difficulties in handling and application to the skin as intended.
For this problem, an external preparation kit with which two or more different sheets are laminated and applied to the skin has been proposed.
For example, Patent Literature 4 (Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2009-541301) discloses a treatment article with which, by covering the entire face with a water-insoluble base such as nonwoven fabric after the above described dry film (water-soluble film) type sheet is attached to a part of the face that needs intensive care, the film is dissolved by the water contained in the nonwoven fabric.
In addition, Patent Literature 5 (Japanese Unexamined Patent Application Publication No. 2006-56804) discloses a mask sheet which has a dried water-soluble film containing a beauty component and a gel sheet laminated on the film and with which the liquid in the gel sheet moves to dissolve the water-soluble sheet and the beauty component is dissolved.
Moreover, Patent Literature 6 (Japanese Unexamined Patent Application Publication No. S63-297320) describes a composite patch with which a hydrogel composed of a water-soluble polymer such as polyacrylic acid, polyvinyl alcohol, and polyvinylpyrrolidone and water is placed on a sheet-formed water-soluble drug-containing hydrophilic base for achieving attachment by adhering and layering on the skin.